Diffusion-controlled reference material for VOC emissions testing: proof of concept Introduction Exposures related to indoor sources of volatile organic compounds (VOC) such as building materials, con- sumer products, and office equipment have been linked to occupant discomfort, illness (Boeglin et al., 2006; Mølhave, 1991; Rennix et al., 2005; Wolkoff and Nielsen, 2001), and reduced worker productivity (Bako-Biro et al., 2004; Fanger, 2006). Indoor VOC levels associated with these sources can be reduced by increasing outdoor air ventilation rates, but this entails increased costs for building construction, operation, and energy. As a result, low VOC-emitting products are being promoted and used more widely in buildings to help achieve healthier and more productive indoor environments. Building rating systems, such as the US Green Building CouncilÕs (USGBC) Leadership in Energy and Environmental Design (USGBC, 2009), encourage the use of low emitting building products by rewarding credits for buildings that incorporate these products in their construction. To demonstrate com- pliance, manufacturers frequently submit products to independent laboratories for VOC emissions testing. Typically, these laboratories conduct emissions mea- surements following standard methods on a portion of the product in small-scale chambers with environmen- tal conditions similar to a real building. The uncer- tainties involved in these measurements are not well established, and there is concern that results for the same materials may vary significantly when tested by Abstract Because of concerns about indoor air quality, there is growing aware- ness of the need to reduce the rate at which indoor materials and products emit volatile organic compounds (VOCs). To meet consumer demand for low emit- ting products, manufacturers are increasingly submitting materials to indepen- dent laboratories for emissions testing. However, the same product tested by different laboratories can result in very different emissions profiles because of a general lack of test validation procedures. There is a need for a reference material that can be used as a known emissions source and that will have the same emission rate when tested by different laboratories under the same conditions. A reference material was created by loading toluene into a polymethyl pentene film. A fundamental emissions model was used to predict the toluene emissions profile. Measured VOC emissions profiles using small-chamber emissions tests compared reasonably well to the emissions profile predicted using the emissions model, demonstrating the feasibility of the proposed approach to create a diffusion-controlled reference material. S. S. Cox 1 , Z. Liu 1 , J. C. Little 1 , C. Howard-Reed 2 , S. J. Nabinger 2 , A. Persily 2 1 Department of Civil and Environmental Engineering, Virginia Tech, Durham Hall, Blacksburg, VA, USA, 2 National Institute of Standards and Technology, Bureau Drive, Gaithersburg, MD, USA Key words: Diffusion model; Emission testing; Interlaboratory study; Reference material; Volatile organic compounds. J. C. Little Department of Civil and Environmental Engineering Virginia Tech, 418 Durham Hall Blacksburg, VA 24061-0246, USA Tel.: (540) 231 8737 Fax: (540) 231 7916 e-mail: jcl@vt.edu Received for review 2 February 2010. Accepted for publication 6 May 2010. Practical Implications To calibrate emissions test chambers and improve the reproducibility of VOC emission measurements among different laboratories, a reference material has been created using a polymer film loaded with a representative VOC. Initial results show that the filmÕs VOC emission profile measured in a conventional test chamber compares well to pre- dictions based on independently determined material/chemical properties and a fundamental emissions model. The use of such reference materials has the potential to build consensus and confidence in emissions testing as well as Ôlevel the playing fieldÕ for product testing laboratories and manufacturers. Indoor Air 2010; 20: 424–433 www.blackwellpublishing.com/ina Printed in Singapore. All rights reserved Ó 2010 John Wiley & Sons A/S INDOOR AIR doi:10.1111/j.1600-0668.2010.00666.x 424